Method and apparatus for continuously removing burrs from objects

ABSTRACT

A device for removing burrs from objects thermally insulated from the ambient air consists of subjecting the objects to a blast of granular shot, which is re-cycled after separating-out the removed burrs and is led back to a storage hopper, the shot being continuously insulated thermally from the ambient air and being cooled, simultaneously with the objects by a cold gas in the liquefied form or in course of vaporization. The apparatus comprises a shot-blasting chamber in the form of a heat-insulated tunnel containing a continuously moving conveyor belt on which the objects are disposed.

United States Patent Moret 'et al.

[ July 23, 1974 METHOD AND APPARATUS FOR CONTINUOUSLY REMOVING BURRSFROM OBJECTS Inventors: Bernard Moret, Bondy; Jean-Louis Dufetele, SaintEtienne du Rouvray, both of France Assignee: LAir Liquide, SocieteAnonyme Pour LEtude Et LExploitation Des Procedes Georges Claude, Paris,France Filed: Feb. 23, 1973 Appl. No.: 335,317

Foreign Application Priority Data Feb 29, 1972 France 72.06765 U.S.Cl51/9, 5l/14,51/321, 51/322 Int. Cl. 1324c 3/14, B240 5/00 Field ofSearch 51/8, 9, 14, 319-321, 51/322 [56] References Cited UNITED STATESPATENTS 2,073,184 3/1937 Schwietzer 51/14 2,996,846 8/1961 Leliaert51/322 X 3,110,983 11/1963 Moore 51/9 Primary Examiner-Donald G. KellyAttorney, Agent, or Firm-Young & Thompson [5 7 ABSTRACT A device forremoving burrs from objects thermally insulated from the ambient airconsists of subjecting the objects to a blast of granular shot, which isre cycled after separating-out the removed burrs and is led back to astorage hopper, the shot being continuously insulated thermally from theambient air and being cooled, simultaneously with the objects by a coldgas in the liquefied form or in course of vaporization. The apparatuscomprises a shot-blasting chamber in the form of a heat-insulated tunnelcontaining a continuously moving conveyor belt on vvhich the objectsaredisposed.

4 Claims, 1 Drawing Figure METHOD AND APPARATUS FOR CONTINUOUSLYREMOVING BURRS FROM OBJECTS The present invention relates to a method oftrimming or removing burrs from objects which are thermally insulatedfrom the ambient air, by subjecting them to a mechanical action afterthey have been cooled, at least on their surface, to below C.

Removal of burrs is generally carried out, either by hand with the aidof chisels, various kinds of cutting tools, rotary brushes, or bymachine but in a noncontinuous manner, in rotating tumbling-drums or invibrating machines. The objects may be cooled in order to render theirburrs brittle at the ordinary temperature.

These operations are always non-continuous and therefore necessitate acertain amount of labour, and they are relatively slow. When the effectof cold is utilized to make the burrs brittle, it has been consideredsufficient up to the present time to carry out a simple separation ofthe burrs from the granular shot which is re-cycled to a hoppersupplying the projection apparatus of the shot, while ensuring that theshot remains thermally insulated from the ambient air. It has provedhowever that this method of working is not really appropriate to ensurea good effect of the shot on the objects, and it hasbeen establishedthat the shot was insufficiently cooled.

The method according to the invention utilizes a cryogenic gas in theliquid form, if so desired in course of vaporizatiomin order to cool theobjects and the shot simultaneously. r

Experience has shown the excellent co-operation between a re-liquefiedgas and granular shot, in the sense that it is very easy to inject theliquefied gas into a shotstorage hopper and to cause the vapours of thisliquefied gas to pass through the grains of the shot. Another object ofthe invention is to make the operations both automatic and continuous.

The invention is further characterized in that the objects are caused tocirculate in a continuous movement in contact with a cooling agent,after which their surfaces are treated, with a mechanical burr-removingagent in the form of a jet of granular shot. j

The accompanying drawing shows diagrammatically and by way'ofnon-limitative example, one form of embodiment of the invention.

Inside a thermally-insulated tunnel 2, the downstream extremity of whichforms a shot-blasting chamber, an endless belt 4 circulatescontinuously. This belt may be of very varied nature, for example ofmetallic fabric or of plates articulated on each other.

The objects to be trimmed (not shown) represented symbolically beforetreatment by an arrow 6, are

brought -in on to the upperside of the endless belt after passing over asloping face 8. They are then cooled by a system which can deliver aliquefied gas, for example a liquefied permanent gas, a halogenatedhydrocarbon with a low boiling point, or initially liquefied carbondioxide a cold brine a gas cooled by a frigorifle or cryogenic set thevapours of a cryogenic liquid such as liquid nitrogen, etc.

The objects then pass under jets of shot projected by a wheel enclosedin a casing 12 and which is itself cold. At the same time, they areagitated by a vibrator 14 which shakes the belt and changes theorientation of the objects so that they are attacked by the shot atvari- 18. The sloping face may be replaced by a device arranged lowerand on which the objects are delivered from the belt.

The shot having acted and the removed burrs having fallen into arecovery tank 20, are then led into a separator 22. This separator, asieve or pneumatic separator for example, separates the shot from thefragments of burrs which are evacuated through a tube 24, the shotpassing through a conduit 26 to a raising device 28. This latter may beof various kinds: chain and scoops, inclined belt, endless screw, etc.

From the device 28 the shot is led through a conduit 30 to a hopper 32in which the shot is stored before being sent to the projection wheel inthe casing 12. In the hopper, the shot is cooled, for example byextracting through a tube 34 a cooling fluid contained in a tank 36which also supplies the system 10. This fluid is for example liquidnitrogen.

It will be noted that the whole of the shot recycling circuit, such asthe separator 22, conduit 26, raising device 28, conduit 30, hopper 32,is thermally insulated from the ambient atmosphere, for example byplacing this circuit in an insulated chamber (not shown in the drawing).

When the refrigerant fluid becomes vaporized in contact with theobjects, it emits abundant cold vapours. These vapours escape throughthe extremities of the tunnel, those escaping towards the left servingto effect a pre-cooling of the objects. The quantity of vapour escapingthrough the right-hand extremity can be reduced by fixing at theright-hand extremity 38 of the tunnel cover, a hanging curtain made ofstrips of plastic material which remain flexible in the cold state.

It is useful to vary the conditions of operation of this deviceaccording to the nature and the dimensions of the objects to be trimmed,according to their weight treated per hour, etc. In addition to thenature of the cooling fluid and of its temperature, it is possible alsoto act on:

the flow-rate of this fluid; r

the speed of the travelling belt, which can be controlled by a speedtake-off 30 and an indicator 42;

the delivery rate of shot, controlled for example by a tachometer 44which measures the speed of a motor 46 actuating the raising device.

These parameters can be controlled by a perforatedcard programmingdevice, for which there have been provided as many cards or columns on asingle card as there are types of treatment.

There may also be provided with advantage:

One or a number of temperature tappings in the tunnel, with temperaturedetector 48 and indicator 50.

A temperature tapping in the storage hopper, with indicator 52 and adetector; this tapping may directly control the inlet of cold fluidthrough the tube 34, if so required to give a temperature shown on theprogramming device.

The orientation of the objects may be modified between two shot-blastingperiods, for example by oblique surfaces, by push-rods, or alternativelyby bringing them on to a second suitably orientated belt.

The cooling system may be constituted by the whole of a first device,from which passes out a cold fluid, and of a second device, drawing-inthis fluid through the objects to be cooled and bringing it back to thefirst, after cooling.

The device described may be modified without thereby departing from thescope of the present invention. For example, it may employ a number ofcooling devices, several machines for projecting shots, and rotatingbrushes. The device actuating the burr-removal agent may be givenmovements which change its orientation, and the cooling of the shot maybe dispensed with.

The method of the invention is especially applicable to the removal ofburrs from a large quantity of objects of the same type. It can even beemployed for parts having a length greater than that of the tunnel. Thenature of these objects may be very diverse, provided that they can berendered brittle on the surface by an inexpensive cooling, such as forexample with liquid nitrogen.

These materials may for example be moulded polyurethane, cellular ornot, a large number of thernoplastic materials, rubber, many metals andalloys. In this way, burrs may be removed from tooling keys, dash boardsfor automobiles, moulded parts of zamak, etc.

What we claim is: I

1. A device for removing burrs from objectsby projection of granularshot on said objects, previously cooled, at least at their surface, ofthe kind comprising a shot-blasting chamber, thermally insulated, meansfor projecting said shot, a re-cycling circuit for the shot projectedfrom said chamber to a hopper adapted to supply said projection means,means for injecting a cryogenic liquid into said chamber, said devicefurther comprising means for injecting said cryogenic fluid into saidshot-recycling circuit, and especially into said supply hopper.

2. A device for continuously removing burrs from objects, as claimed inclaim 1, said device further comprising a chamber in the form of aheat-insulated tunnel said tunnel comprising a conveyor belt incontinuous movement, on which said objects are disposed.

3. A device as claimed in claim 2, said device further comprising meansfor putting said objects into contact with a liquefied gas, and meansfor previously putting said objects into contact with the vapours ofsaid liquefied gas.

4. A device as claimed in claim 2, and further comprising means forcausing said conveyor belt to vibrate at a position in which the objectscarried are subjected to the jet of granular shot.

1. A device for removing burrs from objects by projection of granularshot on said objects, previously cooled, at least at their surface, ofthe kind comprising a shot-blasting chamber, thermally insulated, meansfor projecting said shot, a re-cycling circuit for the shot projectedfrom said chamber to a hopper adapted to supply said projection means,means for injecting a cryogenic liquid into said chamber, said devicefurther comprising means for injecting said cryogenic fluid into saidshot-recycling circuit, and especially into said supply hopper.
 2. Adevice for continuously removing burrs from objects, as claimed in claim1, said device further comprising a chamber in the form of aheat-insulated tunnel said tunnel comprising a conveyor belt incontinuous movement, on which said objects are disposed.
 3. A device asclaimed in claim 2, said device further comprising means for puttingsaid objects into contact with a liquefied gas, and means for previouslyputting said objects into contact with the vapours of said liquefiedgas.
 4. A device as claimed in claim 2, and further comprising means forcausing said conveyor belt to vibrate at a position in which the objectscarried are subjected to the jet of granular shot.